<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-08-03</periodOfReport>

    <issuer>
        <issuerCik>0001525221</issuerCik>
        <issuerName>Bristow Group Inc.</issuerName>
        <issuerTradingSymbol>VTOL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001864765</rptOwnerCik>
            <rptOwnerName>Miller Maryanne</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BRISTOW GROUP INC.</rptOwnerStreet1>
            <rptOwnerStreet2>3151 BRIARPARK DRIVE, SUITE 700</rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode>77042</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-08-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6616</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6616</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Pursuant to the Bristow Group Inc. 2021 Equity Incentive Plan, the reporting person was granted restricted stock units (&quot;RSUs&quot;). Each RSU represents a contingent right to receive one share of common stock of Bristow Group Inc.  The RSUs vest in full on August 3, 2022, subject to the reporting person's continued status as a director of Bristow Group Inc. as of the vesting date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Justin D. Mogford, attorney-in-fact for Maryanne Miller</signatureName>
        <signatureDate>2021-08-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
